N | C # program to find the N - th term in 1 , 11 , 55 , 239 , 991 , ... . ; Function to find the N - th term ; calculates the N - th term ; Driver Code
using System ; class GFG { static int numberSequence ( int n ) { int num = ( int ) ( Math . Pow ( 4 , n ) - Math . Pow ( 2 , n ) ) - 1 ; return num ; } public static void Main ( ) { int n = 4 ; Console . WriteLine ( numberSequence ( n ) ) ; } }